Pneumatic tire

ABSTRACT

A pneumatic tire that can be manufactured according to the conventional method without requiring special tire manufacturing steps and without needing addition of material members and production steps, and having excellent rolling resistance and wet properties, and having conductivity is to be provided. A pneumatic tire  10  comprises a carcass  14 , a rim strip  19 , and a wing  24  in which one edge thereof is contacted with the carcass  14  and the other edge thereof is exposed to the surface of a ground contact edge region of a tread part  13 , wherein a carcass ply  14  contacting the rim strip  19  and the wing  24  has a conductive ply  14 X and a nonconductive ply  14 Y on the circumference of the tire, and the conductive ply  14 X and the rim strip and the wing form a continuous conductive path comprising a conductive rubber material, only the conductive path is used as a conducting path of the tire, and members other than the conducting path are selected and used from a conductive rubber material or a nonconductive rubber material.

TECHNICAL FIELD

The present invention relates to a pneumatic tire. More particularly,the invention relates to a pneumatic tire manufactured by theconventional process, that has a tread of silica compounding or thelike, improves rolling resistance and wet properties of a tire, and candischarge static electricity charged in vehicles to road surface.

BACKGROUND ART

To improve rolling resistance and running performance (wet properties)on wet road surface of a pneumatic tire, the technology of compoundingsilica with a rubber composition of a tread as a reinforcing agent inplace of the conventional carbon black is known. With this silicacompounding technology, static electricity charged in vehicles givesrise to the problems that discharge phenomenon is generated when a tirepasses on manholes and the like, resulting in radio noise, adverseinfluence to electronic circuit parts, generation of short-circuit, andthe like.

Conventionally, to solve those problems, the technology of providing aconductive member having carbon black compounded therein in a part of atread structure, thereby securing conductivity of a tire is proposed.For example, the technology of Patent Document 1 below describes that aconductive thin film containing carbon black is arranged on the outersurfaces of a tread and a side wall, thereby discharging through thisconductive layer. Furthermore, the technology of Patent Document 2discloses that a conductive insert is provided on a tire crown part overfrom a tread surface to a bottom, and a conductive strip comprising aconductive material being in contact with this insert is in a contactstate with a wheel in a conductive bead region, thereby dischargingstatic electricity.

Patent Document 1: JP-A-8-230407

Patent Document 2: JP-A-2006-143208

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

However, the technology of Patent Document 1 is that improvement effectson rolling resistance and wet properties of a tread by silicacompounding are decreased by arranging the above-described conductivethin film containing carbon black, and it is difficult to sufficientlyexhibit the original effect. Furthermore, from that the conductive thinfilm containing carbon black is arranged on the outer surfaces of atread and a side wall, additional material members and process steps arerequired, and deterioration of productivity and increase in costs arepredicted.

The technology of Patent Document 2 requires to separately providingconductive insert and strip. Therefore, the number of members isincreased, and special process steps are required. Thus, it is difficultto say that such a tire has a structure that is easily produced, anddecrease in productivity is predicted.

In view of the above problems, the object of the invention is to providea pneumatic tire, that can be manufactured according to the conventionalprocess without requiring special tire manufacturing steps and withoutneeding addition of material members and process steps, has excellentrolling resistance and wet properties, and has conductivity.

Means for Solving the Problems

The invention described in claim 1 is a pneumatic tire comprising acarcass having at least one carcass ply which is turned back and lockedaround a bead core embedded in each of a pair of bead parts, a rim stripprovided in the bead part and contacting with a rim and the carcass, anda wing in which one edge thereof is contacted with the carcass and theother edge thereof is exposed to the surface of a ground contact edgeregion of a tread part, characterized in that at least a carcass plycovering rubber at the contact face side to the rim strip and the winghas a conductive ply comprising a conductive rubber material and anonconductive ply comprising a nonconductive rubber material on thecircumference of the tire, and the conductive ply and at least the rimstrip and the wing in either one side part form a continuous conductivepath comprising a conductive rubber material, only the conductive pathis used as a conducting path of the tire, and members other than theconducting path are selected and used from a conductive rubber materialor a nonconductive rubber material.

The invention claimed in claim 2 is the pneumatic tire as claimed inclaim 1, characterized in that the conductive ply occupies from 10 to50% of the circumferential length of the tire over between a pair of thebead parts.

The invention claimed in claim 3 is the pneumatic tire as claimed inclaim 1 or 2, characterized in that the carcass comprises at least onecarcass ply which is turned back from the inside of the tire to theoutside thereof around a pair of the bead cores and locked, both frontand back faces of the carcass ply are covered with the conductiverubber, and the turned back portion of the carcass ply is contacted withthe rim strip.

The invention claimed in claim 4 is the pneumatic tire as claimed inclaim 1 or 2, characterized in that the carcass comprises at least onefirst carcass ply which is turned back from the inside of the tire tothe outside thereof around a pair of the bead cores and locked, and asecond carcass ply which reaches the bead part through a side wall partfrom the tread part, contacts with the rim strip, and is locked, and asecond carcass ply covering rubber of a tire outside face of the secondcarcass ply comprises a conductive rubber material.

The invention claimed in claim 5 is the pneumatic tire as claimed inclaim 1 or 2, characterized in that the carcass comprises at least onecarcass ply which is turned back from the inside of the tire to theoutside thereof around a pair of the bead cores and locked, and thecarcass ply at the inner face side of the carcass is extended to thewing outward in a radial direction of the tire while contacting with therim strip to contact with the wing, and is locked, in the turned backportion.

The invention claimed in claim 6 is the pneumatic tire as claimed in anyone of claims 1 to 5, characterized in that the conductive rubbermaterial is a rubber composition having electric resistivity less than10⁸ Ω·cm.

The invention claimed in claim 7 is the pneumatic tire as claimed inclaim 6, characterized in that the conductive rubber material comprisesa rubber composition comprising a diene rubber as a rubber component,and carbon black having a nitrogen adsorption specific area of from 25to 100 m²/g is contained in an amount of 14 vol % or more of the entirerubber composition.

The invention claimed in claim 8 is the pneumatic tire as claimed inclaim 1, characterized in that the nonconductive rubber materialcomprises a rubber composition containing a non-carbon black reinforcingagent as a reinforcing agent.

The invention claimed in claim 9 is the pneumatic tire as claimed inclaim 8, characterized in that the non-carbon black reinforcing agent issilica.

Advantage of the Invention

By forming a continuous conductive path on a part of the circumferenceof a tire by utilizing a conductive carcass ply, and using only theconductive path as a conducting path of the tire, the pneumatic tire ofthe present invention can provide a tire having conductivity whileadditionally having excellent rolling resistance and wet properties dueto silica compounding, that can be manufactured by the conventionalprocess without requiring any special tire manufacturing step asdisclosed in the prior art, and without needing addition of materialmembers and process steps, and can eliminate problems such as noises,adverse influence to electronic parts, and short-circuit, due to staticelectricity charged in vehicles using a nonconductive tire of silicacompounding or the like.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention are described below.

First Embodiment

FIG. 1 is a semi-sectional view showing a pneumatic tire 10 of a firstembodiment of the invention.

The pneumatic tire (hereinafter, the pneumatic tire is simply referredto as a “tire”) 10 comprises a carcass 14 comprising one carcass ply 25which is turned back from the inside of the tire to the outside thereofaround a bead core 12 embedded in each of a pair of the bead parts 11,and locked, a tread part 13 located at an outer circumferential side ina radial direction of the tire of the carcass 14, a side wall part 16located at the side part of the carcass 14, and a belt 18 comprising twocrossed belt plies provided inward the tread part 13 and between thetread part 13 and the carcass 14.

The tire 10 has a rim strip 19 provided outward in an axial direction ofthe tire of the bead part 11, and the outside face of a rim strip rubber23 is contacted with a rim, and the inside face thereof is contactedwith a turned back portion 14 a of the carcass ply 25.

The tire 10 has a side wall-on-tread (SWOT) structure in which theoutward edge in a radial direction of the tire of the side wall part 16is overlapped on both edges of a crown part 15 constituting a mainground contact part in the tread part 13, as shown in FIG. 1.Specifically, the outward edge of the side wall part 16 covers thesurface of both peripheral parts of the tread part 13 on thecircumference of the tire to form a shoulder part 17 constituting atread ground contact edge region.

In the shoulder part 17, a wing 24 in which an upper edge thereof isexposed to the surface of the tread ground contact edge region andcontacted with road surface, and the lower edge thereof is contactedwith the carcass ply 25 is provided between both edges of a tread rubber21 and the outward edge in a radial direction of the tire of a side wallrubber 22.

Therefore, the carcass ply 25 turns back around the bead core 12 throughthe side wall part 16 while contacting with the lower edge of the wingrubber 24 over from the tread part 13 to the shoulder part 16, and iscontacted with the tire inner face side of the rim strip rubber 23, anda ply turned back edge 14 a is locked in the side wall part 16. By this,the rim strip 19 and the wing 24 are continuously connected through acarcass ply 14.

Furthermore, the tire 10 shows a tire for passenger car having a radialstructure having a belt 18 comprising two crossed belt plies providedinside the tread part 13, and one cap ply 20 comprising a cord helicallywound at an angle of nearly 0° to a circumferential direction of thetire, on the outer circumference of the belt 18.

An organic fiber cord such as polyester, nylon or rayon is used in thecarcass ply 25 as a reinforcing material, a rigid cord such as steelcord or aramide fiber is used in a belt ply of the belt 18 as areinforcing material, and a cord having relatively large heatshrinkability such as nylon or polyester is used in a cap ply 20 as areinforcing material.

A rubber composition using non-carbon black reinforcing agents such assilicas such as precipitated silica or silicic anhydride, clays such ascalcined clay or hard clay, and calcium carbonate as a reinforcing agentin place of the conventional carbon black as a reinforcing agent is usedin a tread rubber 21 constituting the crown part 15 corresponding to amain ground contact part of the tread part 13 so as to decrease tan δ ofa rubber composition in order to contribute to the improvement ofrolling resistance and wet properties of the tire 10. Silica havinglarge improvement effect on rolling resistance and the like isparticularly preferably used.

In those non-carbon black rubber compositions, the compounding amount ofthe non-carbon black reinforcing agent such as silica is generally from30 to 100 parts by weight, and preferably from 40 to 80 parts by weight,per 100 parts by weight of the rubber component, although varyingdepending on the kind and the substitution amount of carbon black.

In the case of silica, the kind of silica is not particularly limited.Wet silica having nitrogen adsorption specific area (BET) of from 100 to250 m²/g and DBP oil absorption of 100 ml/100 g or more is preferred inreinforcing effect and processability, and the commercially availableproducts such as NIPSIL AQ and VN3, manufactured by Tosoh SilicaCorporation, and ULTRASIL VN3, manufactured by Degussa can be used.Furthermore, the combination use of a silane coupling agent such asbis(triethoxysilylpropyl)-tetrasulfide is preferred.

As carbon black in the tread rubber 21, SAF, ISAF, HAF and the like arepreferred in abrasion resistance and exothermic properties.

Diene rubbers such as natural rubber (NR), isoprene rubber (IR),styrene-butadiene rubber (SBR) and butadiene rubber (BR) are generallyused as a rubber component in the rubber composition of the tread rubber21. Those are used alone or as a blend rubber. Furthermore, oils ofrubber compounding agent, softeners such as wax, stearic acid, zincwhite, resins, age resistors, vulcanizing agents such as sulfur,vulcanization accelerators, and the like are appropriately compounded.

Furthermore, to enhance the improvement effects such as rollingresistance, a rubber composition containing the non-carbon blackreinforcing agent as a reinforcing agent in an amount of from 30 to 100parts by weight per 100 parts by weight of the rubber component is usedin a side wall rubber 22 of the side wall part 16, simultaneously withthe tread rubber.

The nonconductive side wall 22 is obtained by containing diene rubberssuch as NR, IR, SBR, BR or butadiene rubber (VCR) containingsyndiotactic-1,2-polybutadiene, alone or as blends thereof, as a rubbercomponent, and carbon black having nitrogen adsorption specific surfacearea (N₂SA) of from 25 to 100 m²/g in an amount less than 14 vol % ofthe entire rubber composition.

Furthermore, where N₂SA of carbon black is less than 25 m²/g, durabilityis decreased due to decrease in strength of the rubber composition, andwhere N₂SA exceeds 100 m²/g, hysteresis loss is increased, resulting inincrease in rolling resistance and generation of heat.

Carbon black having N₂SA of from 25 to 100 m²/g includes carbon blacksof HAF, FEF and GPF grades.

Non-carbon black reinforcing agent such as silica, clay or calciumcarbonate may be used in an appropriate amount in combination withcarbon black. Furthermore, oils of rubber compounding agent, softenerssuch as wax, stearic acid, zinc white, resins, age resistors,vulcanizing agents such as sulfur, vulcanization accelerators, and thelike are appropriately compounded.

By this, the tread rubber 21 and the side wall rubber 22 improve rollingresistance and wet properties, but on the other hand, the rubbercompositions have electric resistivity of 10⁸ Ω·cm or more, and formnonconductive rubbers. As a result, the tire 10 becomes nonconductive,and becomes a nonconductive tire having electric resistance of 10⁹Ω ormore by the combination of each member, and static electricity chargedin vehicles cannot be discharged to road surface from the tread part 13.

To solve the problem on static electricity charged in vehicles, the tire10 of the present embodiment is formed such that a conductive rubber ora nonconductive rubber is applied to at least a covering rubber (toppingrubber) of the carcass ply 25 at a contact face side to the rim strip 19and the wing 24, the topping rubber has a conductive ply 14X comprisinga conductive rubber and a nonconductive ply 14Y comprising anonconductive rubber on the circumference of the tire between the beadparts 11, 11, and a conductive rubber having electric resistivity lessthan 10⁸ Ω·cm is applied to the rim strip rubber 23 and the wing rubber24 in at least either one side part.

The tire 10 of the present embodiment is that as shown in a tire sideview of FIG. 2 in which the side wall rubber 22 was cut off, aconducting path reaching the wing rubber 24 through the rim strip rubber23 and the topping rubber of the conductive ply 14X from the rim isformed by providing the conductive ply 14X on a part of thecircumference of the tire, and static electricity of vehicles can bedischarged to road surface from the upper edge of the wing rubber 24exposed to the surface of the shoulder part 17 and contacted with theroad surface.

The conductive ply 14X may be arranged on one place of 14X1 on thecircumference of the tire, and may be dividedly arranged on two placesof 14X1 and 14X2, or more than two places. However, where the number ofdivision is increased, the number of fabricating steps of a green tireis increased, resulting in decrease in productivity.

Furthermore, it is preferred that the proportion of the conductive ply14X occupied in the carcass ply 25 is from 10 to 50% of thecircumferential length of the tire over between beads 11, 11. That is,the ply formed between beads 11, 11 is changed to the conductive ply 14Xin a proportion of from 10 to 50% of carcass area of the tire innerface, and in a circumferential length of from 10 to 50% of thecircumferential length of the tire. Where the proportion of theconductive ply is less than 10%, conductivity of the tire is deficient,resulting in decrease in discharge properties of static electricity.Where the proportion exceeds 50%, the amount of the conductive rubberused is increased, affecting the improvement of rolling resistance.

By this, the topping rubber of the conductive ply 14X and the wingrubber 24 are formed into a continuous conductive path from the rimstrip rubber 23.

The tire 10 uses only the conductive path as a conducting path, andstatic electricity charged in vehicles can be discharged to road surfacefrom the upper edge of the wing rubber 24 exposed to the surface of theshoulder 17 and contacting with the road surface through the rim striprubber 23 and the topping rubber of the carcass ply 25 from the rim.

A method for applying the conductive ply 14X to the tire is notparticularly limited, but a method of jointing the nonconductive ply 14Yand the conductive ply 14X on a molding drum at the time of fabricatinga green tire, and forming the carcass ply 25 is simple and easy.Furthermore, the carcass ply 25 may be produced by cutting a toppingsheet and alternately jointing the conductive ply 14X and thenonconductive ply 14Y in a given width in a jointing process.

The conductive rubber composition can easily be obtained byappropriately adjusting the compounding amount of carbon black, and itis desired that the rubber composition has electric resistivitypreferably less than 10⁷ Ω·cm.

The conductive topping rubber is obtained by containing diene rubberssuch as NR, IR, SBR, BR or butadiene rubber (VCR) containingsyndiotactic-1,2-polybutadiene, alone or as blends thereof, as a rubbercomponent, and carbon black having nitrogen adsorption specific surfacearea (N₂SA) of from 25 to 100 m²/g in an amount of 14 vol % or more ofthe entire rubber composition.

Where the amount of carbon black is less than 14 vol %, electricresistivity of the rubber composition is 10⁸ Ω·cm or more, resulting indeterioration of conductivity. Furthermore, where N₂SA of carbon blackis less than 25 m²/g, durability is decreased due to decrease instrength of the rubber composition, and where N₂SA exceeds 100 m²/g,hysteresis loss is increased, resulting in increase in rollingresistance and generation of heat.

Carbon black having N₂SA of from 25 to 100 m²/g includes carbon blacksof HAF, FEF and GPF grades.

Non-carbon black reinforcing agent such as silica, clay or calciumcarbonate may be used in an appropriate amount in combination withcarbon black. Furthermore, oils of rubber compounding agent, softenerssuch as wax, stearic acid, zinc white, resins, age resistors,vulcanizing agents such as sulfur, vulcanization accelerators, and thelike are appropriately compounded.

In the present embodiment, by contacting the tire outer face side of theconductive ply 14X with the lower edge of the wing rubber 24 andcontacting the tire inner face side of the ply 14X with the inner faceside of the rim strip rubber 23 after turning back the bead core 12,electricity is passed through the topping rubber of the conductive ply14X. Therefore, it is necessary to apply a conductive rubber to thetopping rubbers of both the front and back faces of the ply 14X.

The carcass ply 25 is obtained by subjecting both sides of anadhesive-treated tire cord fabric obtained by weaving an organic fibercord with given counts to topping processing using a conductive rubberor a nonconductive rubber in a given rubber thickness using a calenderapparatus for fiber cord generally used in tire industries, having Ztype calender or two tandem-arranged three-roll calenders by theconventional method. The carcass ply can similarly be obtained in thefollowing embodiments.

The conductive rim strip rubber 23 contains diene rubbers such as NR,IR, SBR, BR or VCR alone or as blends thereof, as a rubber component,and carbon black having N₂SA of from 70 to 100 m²/g in an amount of 14vol % or more of the entire rubber composition.

Where the amount of carbon black is less than 14 vol %, electricresistivity of the rubber composition is 10⁸ Ω·cm or more, resulting indeterioration of conductivity. Furthermore, where N₂SA of carbon blackis less than 70 m²/g, the bead part is liable to be damaged due to rimrubbing by decrease in abrasion resistance of the rubber composition,and where N₂SA exceeds 100 m²/g, hysteresis loss deteriorates, resultingin increase in rolling resistance and generation of heat.

Carbon black having N₂SA of from 70 to 100 m²/g includes carbon black ofHAF grade.

Non-carbon black reinforcing agent such as silica, clay or calciumcarbonate may be used in an appropriate amount in combination withcarbon black. Furthermore, oils of rubber compounding agent, softenerssuch as wax, stearic acid, zinc white, resins, age resistors,vulcanizing agents such as sulfur, vulcanization accelerators, and thelike are appropriately compounded.

The conductive wing rubber 24 comprises a rubber composition containingdiene rubbers such as NR, IR, SBR, BR or VCR alone or as blends thereof,as a rubber component, and carbon black having N₂SA of from 25 to 100m²/g in an amount of 14 vol % or more of the entire rubber composition.

Where the amount of carbon black is less than 14 vol %, electricresistivity of the rubber composition is 10⁸ Ω·cm or more, resulting indeterioration of conductivity. Furthermore, where N₂SA of carbon blackis less than 25 m²/g, durability is decreased due to decrease instrength of the rubber composition, and where N₂SA exceeds 100 m²/g,hysteresis loss deteriorates, resulting in increase in rollingresistance and generation of heat.

Carbon black having N₂SA of from 25 to 100 m²/g includes carbon blacksof HAF, FEF and GPF grades.

Non-carbon black reinforcing agent such as silica, clay or calciumcarbonate may be used in an appropriate amount in combination withcarbon black. Furthermore, oils of rubber compounding agent, softenerssuch as wax, stearic acid, zinc white, resins, age resistors,vulcanizing agents such as sulfur, vulcanization accelerators, and thelike are appropriately compounded.

In the present embodiment, the conductive ply 14X interconnecting theright and left bead parts 11, 11 is used as a conducting path.Therefore, it is sufficient only if the conductive rim strip 19 and wing24 are provided on at least either one tire side part, and thearrangement is not particularly limited. That is, when the conductiverim strip 19 and wing 24 are provided on every either one tire sidepart, discharge properties of static electricity using the carcass ply25 as a conducting path can be secured.

The arrangement examples of the conductive rim strip 19 and wing 24 arespecifically described below. (1) The conductive rim strip and wing arearranged at both side parts of the tire. (2) The conductive rim stripand wing are arranged at only one side part, and nonconductive rim stripand wing are applied to other side part. (3) A conductive rim strip anda nonconductive wing are arranged at one side part, and a nonconductiverim strip and a conductive wing are applied to other side part.Alternatively, the reverse arrangement is employed.

That is, the case (1) that a conductive rubber is applied to the rimstrip rubber 23 and the wing rubber 24 at both side parts of the tire 10is preferred in the standpoint that conductivity of a tire is increased.Although electric resistance of a tire is slightly increased by thearrangements (2) and (3) above, conductivity of a tire can be securedand there is no practical problem. By this, rolling resistance and wetproperties of the tire 10 can be improved by increasing the amount ofthe nonconductive rubber used.

The nonconductive rim strip rubber 23 is obtained by changing only thecompounding amount of carbon black in the conductive rubber. That is,the nonconductive rim strip rubber 23 is a rubber composition containingcarbon black having N₂SA of from 70 to 100 m²/g in an amount less than14 vol % of the entire rubber composition. Where the amount of carbonblack is 14 vol % or more, electric resistivity of the rubbercomposition is less than 10⁸ Ω·cm, and the rubber composition hasconductivity. However, improvement in rolling resistance is notobtained.

The nonconductive wing rubber 24 is obtained by changing only thecompounding amount of carbon black in the conductive wing rubber. Thatis, the nonconductive wing rubber 24 is a rubber composition containingcarbon black having N₂SA of from 25 to 100 m²/g in an amount less than14 vol % of the entire rubber composition. Where the amount of carbonblack is 14 vol % or more, electric resistivity of the rubbercomposition is less than 10⁸ Ω·cm, and the rubber composition hasconductivity. However, improvement in rolling resistance is notsufficiently obtained.

In the tire 10 shown in FIG. 1, the tread rubber 21 shows a tread ofintegrated structure. In the case that the tread part 13 has a cap/basestructure, a nonconductive rubber is applied to a cap rubber from thestandpoints of rolling resistance and wet properties. A base rubber canappropriately be selected from a conductive or nonconductive rubber.Other sites such as a topping rubber of a belt and bead filler canappropriately be selected from a conductive or nonconductive rubber solong as a conducting path is not formed. A nonconductive rubber ispreferably selected from the standpoint of the improvement in rollingresistance and wet properties.

The above embodiment is described on the basis of a one ply structuretire comprising one carcass ply. However, needless to say, the presentinvention can be applied to a tire of a structure of two plies or morein which two or more carcass plies are turned back from the inside ofthe tire to the outside thereof around a bead core and locked. In thiscase, a conductive ply is applied to a ply at an outer face side of atire.

Second Embodiment

FIG. 3 is a semi-sectional view showing a pneumatic tire 30 of a secondembodiment according to the invention.

The tire 30 comprises two plies carcass 34 comprising two carcass plies45, 46, a tread part 33 located at the outer circumferential part in aradial direction 5 of the tire of the carcass 34, a side wall part 36located at the side part of the carcass 34, and a belt 38 comprising twocrossed belt plies provided inward the tread part 33 and between thetread part 33 and the carcass 34.

The tire 30 is that a rim strip 39 is arranged at the outside in anaxial direction of the tire of a bead part 31, an outside face of a rimstrip rubber 43 is contacted with a rim, and the inside face thereof iscontacted with the carcass 34.

The tire 30 has a SWOT structure in which the outside edge in a radialdirection of the tire of the side wall part 36 is overlapped on bothedges of a crown part 35 constituting a main ground contact part in thetread part 33. That is, the outside edge of the side wall part 36 coversthe surface of both circumferential parts of the tread part 33 on thecircumference of the tire, thereby forming a shoulder part 37 becoming atread ground contact edge region.

In the shoulder part 37, a wing 44 in which the upper edge thereof isexposed to the surface of the tread ground contact edge region andcontacted with road surface and the lower edge thereof is contacted withthe carcass 34 is arranged between both edges of a tread rubber 41 andthe outside edge in a radial direction of the tire of the side wallrubber 42.

The carcass 34 constitutes a two-ply tire comprising a first plycomprising one carcass ply 45 which is turned back from the inside ofthe tire to the outside thereof around a bead core 32 embedded in eachof a pair of beads part 31, 31, and locked, and a second ply whichreaches a rim strip 39 of the bead part 31 through a side wall part 36from the tread part 33 and is contacted with the inner face side of arim strip rubber 43, its ply edge 46 a being locked in the bead part 31.

As shown in FIG. 3, the tire 30 of the present embodiment is such thatthe tire outside face of the second ply 46 is contacted with the loweredge of the wing rubber 44 and the inner face side of the rim striprubber 43 between the tread part 33 and the bead part 31. By this, therim strip 39 and the wing 44 are continuously connected through thesecond carcass ply 46.

Furthermore, the tire 30 shows a tire for passenger car having a radialstructure having a belt 38 comprising two crossed belt plies providedinside the tread part 33, and one cap ply 40 comprising a cord helicallywound at an angle of nearly 0° to a circumferential direction of thetire, on the outer circumference of the belt 38.

An organic fiber cord such as polyester, nylon or rayon is used in thecarcass plies 45, 46 as a reinforcing material, a rigid cord such assteel cord or aramide fiber is used in a belt ply of the belt 38 as areinforcing material, and a cord having relatively large heatshrinkability such as nylon or polyester is used in a cap ply 40 as areinforcing material.

In the tire 30, similarly to the tire 10 of the first embodiment, arubber composition using non-carbon black reinforcing agents such assilicas such as precipitated silica or silicic anhydride, clays such ascalcined clay or hard clay, and calcium carbonate as a reinforcing agentin place of the conventional carbon black as a reinforcing agent is usedin a tread rubber 41 of the tread part 33 so as to decrease tan δ of arubber composition in order to contribute to the improvement in rollingresistance and wet properties of the tire 30. Silica having largeimprovement effect on rolling resistance and the like is particularlypreferably used.

The rubber composition of the tread rubber 41 uses a compositioncontaining a non-carbon black reinforcing material such as silica in anamount of generally from 30 to 100 parts by weight, and preferably from40 to 80 parts by weight, per 100 parts by weight of the rubbercomponent, although varying depending on the kind and substitutionamount of carbon black.

Furthermore, to enhance the improvement effects on rolling resistanceand the like, a rubber composition containing the non-carbon blackreinforcing material as a reinforcing material in an amount of from 30to 100 parts by weight per 100 parts by weight of the rubber componentis used in the side wall rubber 42 of the side wall part 36.

Those nonconductive tread rubber 41 and side wall rubber 42 can use therubber composition described in the first embodiment. Therefore, thedescription regarding formulation contents such as its rubber componentand the amount of carbon black is omitted in the present embodiment.

By this, the tread rubber 41 and the side wall rubber 42 improve rollingresistance and wet properties, but on the other hand, the rubbercompositions have electric conductivity of 10⁸Ω·cm or more, and formnonconductive rubbers. As a result, the tire 30 is nonconductive, andbecomes a nonconductive tire having electric resistance of 10⁹Ω or moreby the combination of each member, and static electricity charged invehicles cannot be discharged to road surface from the tread part 33.

To solve the problem on static electricity charged in vehicles, the tire30 of the present embodiment is formed by that a conductive rubber or anonconductive rubber is applied to at least the topping rubber of thetire outside face of the second ply 46 contacting with the rim strip 39and the wing 44, the topping rubber has a conductive ply 46X comprisinga conductive rubber and a nonconductive ply 46Y comprising anonconductive rubber on the circumference of the tire between the beadparts 31, 31, and a conductive rubber having electric conductivity lessthan 10⁸ Ω·cm is applied to the rim strip rubber 23 and the wing rubber24 in at least either one side part.

The tire 30 of the present embodiment is such that as shown in a tireside view of FIG. 4 in which the side wall rubber 42 was cut off, aconducting path reaching the wing rubber 44 through the rim strip rubber43 and the topping rubber of the conductive ply 46X from the rim isformed by providing the conductive ply 46X on a part of thecircumference of the tire, and static electricity of vehicles can bedischarged to road surface from the upper edge of the wing rubber 44exposed to the surface of the shoulder part 17 and contacting with theroad surface.

The conductive ply 46X may be arranged on one place of 46X1 on thecircumference of the tire, and may be dividedly arranged on two placesof 46X1 and 46X2, or more than two places. However, where the number ofdivision is increased, the number of fabricating steps of a green tireis increased, resulting in decrease in productivity.

Furthermore, it is preferred that the proportion of the conductive ply46X occupied in the second ply 46 is from 10 to 50% of thecircumferential length of the tire over between beads 31, 31. That is,the second ply 46 formed between beads 31, 31 is changed to theconductive ply 46X in a proportion of from 10 to 50% of carcass area ofthe tire inner face, and in a circumferential length of from 10 to 50%of the circumferential length of the tire. Where the proportion of theconductive ply is less than 10%, conductivity of the tire is deficient,resulting in decrease in discharge properties of static electricity.Where the proportion exceeds 50%, the amount of the conductive rubberused is increased, affecting the improvement in rolling resistance.

By this, the rim strip rubber 43, the topping rubber of the conductiveply 46X of the second ply 46 and the wing rubber 44 are formed into acontinuous conductive path.

The tire 30 uses only the conductive path as a conducting path, andstatic electricity charged in vehicles can be discharged to road surfacefrom the upper edge of the wing rubber 44 exposed to the surface of theshoulder 17 and contacting with the road surface through the rim striprubber 43 and the topping rubber of the conductive ply 46X of the secondply 46 from the rim.

A conducting path reaching the wing rubber 44 is formed, and staticelectricity charged in vehicles can be discharged to road surface fromthe upper edge of the wing rubber 44 exposed to the surface of theshoulder 37 and contacted with the road surface.

A method for applying the conductive ply 46X to the tire is notparticularly limited, but a method of jointing the nonconductive ply 46Yand the conductive ply 46X on a molding drum at the time of fabricatinga green tire, and forming the second ply 46 is simple and easy.Furthermore, the second ply 46 may be produced by cutting the toppingsheet and alternately jointing the conductive ply 46X and thenonconductive ply 46Y in a given width in a jointing process.

The conductive rubber composition can easily be obtained byappropriately adjusting the compounding amount of carbon black, and itis desired that the rubber composition has electric resistivity ofpreferably less than 10⁷ Ω·cm.

The conductive topping rubber can use the rubber composition for toppingrubber described in the first embodiment. Therefore, the descriptionregarding formulation contents such as its rubber component and theamount of carbon black are omitted in the present embodiment.

In the present embodiment, the tire outer face side of the second ply 46is contacted with the rim strip rubber 43 and the lower edge of the wingrubber 44 to form a conducting path. Therefore, a nonconductive rubbermay be used in the tire inner face side of the second ply 46 and thefirst ply 45.

Even in the present embodiment, the second ply 46 contacting with theinner face side of the right and left rim strips 43 to interconnect thebead parts 31 is used as a conducting path. Therefore, it is sufficientonly if the conductive rim strip 39 and wing 44 are provided in at leasteither one tire side part, and the arrangement is not particularlylimited. That is, when the conductive rim strip 39 and wing 44 areprovided in every either one tire side part, discharge properties ofstatic electricity using the second ply 46 as a conducting path can besecured.

The conductive and nonconductive rubber rubbers used in the rim striprubber 43 and the wing rubber 44 can use the rubber compositiondescribed in the first embodiment. Therefore, the description regardingformulation contents such as its rubber component and the amount ofcarbon black is omitted in the present embodiment.

In the tire 30 shown in FIG. 3, the tread rubber 41 shows a tread ofintegrated structure. In the case that the tread part 33 has a cap/basestructure, a nonconductive rubber is applied to a cap rubber from thestandpoints of rolling resistance and wet properties. A base rubber canappropriately be selected from a conductive or nonconductive rubber.Other sites such as a side wall, a topping rubber of a belt and beadfiller can appropriately be selected from a conductive or nonconductiverubber so long as a conducting path is not formed. A nonconductiverubber is preferably selected from the standpoint of the improvement inrolling resistance and wet properties.

In the above description, the invention is described by the tire havingtwo-ply structure in which one carcass ply 45 is turned back from theinside of the tire to the outside thereof around the bead core andlocked. However, the invention can be applied to the tires having astructure of three or more plies, comprising a first carcass (inner ply)in which two or more carcass plies are turned back from the inside ofthe tire to the outside thereof around the bead core and locked, and asecond carcass (outer ply) reaching the bead part 39 through the sidewall part 36 from the tread part 33.

Third Embodiment

FIG. 5 is a semi-sectional view showing a pneumatic tire 30 of a thirdembodiment.

The tire 50 is equipped with two-ply carcass 54 comprising two carcassplies 65, 66, a tread part 53 located at the outer circumferential sidein a radial direction of the tire of the carcass 54, a side wall part 56located at the side part of the carcass 54, and a belt 58 comprising twocrossed belt plies provided inside the tread part 53 and between thetread part 53 and the carcass 54.

The tire 50 is such that a rim strip 59 is arranged outside in an axialdirection of the tire of the bead part 51, an outside face of a rimstrip rubber 63 is contacted with a rim, and the inside face thereof iscontacted with the carcass 54.

The tire 50 has a SWOT structure in which the outside edge in a radialdirection of the tire of the side wall part 56 is overlapped on bothedges of a crown part 55 constituting a main ground contact part in thetread part 53. That is, the outside edge of the side wall part 56 coversthe surface of both circumferential parts of the tread part 53 on thecircumference of the tire, thereby forming the shoulder part 57 becominga tread ground contact edge region.

In the shoulder part 57, a wing 64 in which the upper edge thereof isexposed to the surface of the tread ground contact edge region andcontacted with road surface and the lower edge thereof is contacted withthe carcass 64 is arranged between both edges of the tread rubber 61 andthe outside edge in a radial direction of the tire of the side wallrubber 62.

The carcass 54 comprises two carcass plies of a first ply 65 and asecond ply 66 which are turned back from the inside of the tire to theoutside thereof around a bead core 52 embedded in each of a pair of beadparts 51, 51, and locked. The second ply 66 is turned back around thebead core 52, and its ply edge 66 a is locked in the bead part 51. Thefirst ply 65 is turned back around the bead core 52 to contact with therim strip 59, and is extended outward in a radial direction of the tirein the side wall part 56 to reach the shoulder part 57, and a ply edge65 a is contacted with a wing 64 and locked. Therefore, the tire 50constitutes a two-ply tire forming the carcass 54 of substantiallythree-ply structure in the side wall 56.

The tire 50 of the present embodiment is that as shown in FIG. 5, thetire outside face of the first carcass ply 65 is contacted with theinner face side of the rim strip rubber 63 and the lower edge of thewing rubber 64 between the bead part 31 and the shoulder part 57 afterturning back the bead core 52. By this, the rim strip 59 and the wing 64are continuously connected through the first ply 65.

Furthermore, the tire 50 shows a tire for passenger car having a radialstructure having a belt 58 comprising two crossed belt plies providedinside the tread part 53, and one cap ply 60 comprising a cord helicallywound at an angle of nearly 0° to a circumferential direction of thetire, on the outer circumference of the belt 58.

An organic fiber cord such as polyester, nylon or rayon is used in thecarcass plies 65, 66 as a reinforcing material, a rigid cord such assteel cord or aramide fiber is used in a belt ply of the belt 58 as areinforcing material, and a cord having relatively large heatshrinkability such as nylon or polyester is used in a cap ply 60 as areinforcing material.

In the tire 50, similarly to the tire 10 of the first embodiment, arubber composition using non-carbon black reinforcing agents such assilicas such as precipitated silica or silicic anhydride, clays such ascalcined clay or hard clay, and calcium carbonate as a reinforcing agentin place of the conventional carbon black as a reinforcing agent is usedin a tread rubber 61 of the tread part 53 so as to decrease tan δ of arubber composition in order to contribute to the improvement of rollingresistance and wet properties of the tire 50. Silica having largeimprovement effect in rolling resistance and the like is particularlypreferably used.

The rubber composition of the tread rubber 61 uses a compositioncontaining a non-carbon black reinforcing material such as silica in anamount of generally from 30 to 100 parts by weight, and preferably from40 to 80 parts by weight, per 100 parts by weight of the rubbercomponent, although varying depending on the kind and substitutionamount of carbon black.

Furthermore, to enhance the improvement effects in rolling resistanceand the like, a rubber composition containing the non-carbon blackreinforcing material as a reinforcing material in an amount of from 30to 100 parts by weight per 100 parts by weight of the rubber componentis used in the side wall rubber 62 of the side wall part 56.

By this, the tread rubber 61 and the side wall rubber 62 improve rollingresistance and wet properties, but on the other hand, the rubbercompositions have electric conductivity of 10⁸ Ω·cm or more, and formnonconductive rubbers. As a result, the tire 50 is nonconductive, andbecomes a nonconductive tire having electric resistance of 10⁹Ω or moreby the combination of each member, and static electricity charged invehicles cannot be discharged to road surface from the tread part 53.

The nonconductive tread rubber 61 and side wall rubber 62 can use therubber composition described in the first embodiment. Therefore, thedescription regarding formulation contents such as its rubber componentand the amount of carbon black is omitted in the present embodiment.

To solve the problem on static electricity charged in vehicles, the tire50 of the present embodiment is formed such that a conductive rubber ora nonconductive rubber is applied to at least the topping rubber of thetire outside face of the first ply 65 contacting with the rim strip 59and the wing 64, the topping rubber has a conductive ply 65X comprisinga conductive rubber and a nonconductive ply 65Y comprising anonconductive rubber on the circumference of the tire between the beadparts 51, 51, and a conductive rubber having electric conductivity lessthan 10⁸ Ω·cm is applied to the rim strip rubber 63 and the wing rubber64 in at least either one side part.

The tire 50 of the present embodiment is such that as shown in a tireside view of FIG. 6 in which the side wall rubber 62 was cut off, aconducting path reaching the wing rubber 64 through the rim strip rubber63 and the topping rubber of the conductive ply 65X from the rim isformed by providing the conductive ply 65X on a part of thecircumference of the tire, and static electricity of vehicles can bedischarged to road surface from the upper edge of the wing rubber 64exposed to the surface of the shoulder part 57 and contacting with theroad surface.

The conductive ply 65X may be arranged on one place of 65X1 on thecircumference of the tire, and may be dividedly arranged on two placesof 65X1 and 65X2, or more than two places. However, where the number ofdivision is increased, the number of fabricating steps of a green tireis increased, resulting in decrease in productivity.

Furthermore, it is preferred that the proportion of the conductive ply65X occupied in the first ply 65 is from 10 to 50% of thecircumferential length of the tire over between beads 51, 51. That is,the first ply 65 formed between beads 51, 51 is changed to theconductive ply 65X in a proportion of from 10 to 50% of carcass area ofthe tire inner face, and in a circumferential length of from 10 to 50%of the circumferential length of the tire. Where the proportion of theconductive ply is less than 10%, conductivity of the tire is deficient,resulting in decrease in discharge properties of static electricity.Where the proportion exceeds 50%, the amount of the conductive rubberused is increased, affecting the improvement of rolling resistance.

By this, the rim strip rubber 63, the topping rubber of the conductiveply 65X of the first ply 65 and the wing rubber 64 are formed into acontinuous conductive path.

The tire 50 uses only the conductive path as a conducting path, andstatic electricity charged in vehicles can be discharged to road surfacefrom the upper edge of the wing rubber 64 exposed to the surface of theshoulder 17 and contacting with the road surface through the rim striprubber 63 and the topping rubber of the conductive ply 65X of the firstply 65 from the rim.

A method for applying the conductive ply 65X to the tire is notparticularly limited, but a method of jointing a nonconductive ply 65Yand the conductive ply 65X on a molding drum at the time of fabricatinga green tire, and forming the first ply 65 is simple and easy.Furthermore, the first ply 65 may be produced by cutting the toppingsheet and alternately jointing the conductive ply 65X and thenonconductive ply 65Y in a given width in a jointing process.

The conductive rubber composition can easily be obtained byappropriately adjusting the compounding amount of carbon black, and itis desired that the rubber composition has electric resistivity ofpreferably less than 10⁷ Ω·cm.

The conductive topping rubber can use the rubber composition for toppingrubber described in the first embodiment. Therefore, the descriptionregarding formulation contents such as its rubber component and theamount of carbon black are omitted in the present embodiment.

In the present embodiment, the tire outer face side of the first ply 65is contacted with the rim strip rubber 63 and the lower edge of the wingrubber 64 to form a conducting path. Therefore, a nonconductive rubbermay be used in the tire inner face side of the first ply 65 and thesecond ply 66.

Even in the present embodiment, the first ply 65 contacting with theinner face side of the right and left rim strips 63 to interconnect thebead parts 51 is used as a conducting path. Therefore, it is sufficientonly if the conductive rim strip 59 and wing 64 are provided in at leasteither one tire side part, and the arrangement is not particularlylimited. That is, when the conductive rim strip 59 and wing 64 areprovided in every either one tire side part, discharge properties ofstatic electricity using the first ply 65 as a conducting path can besecured.

The conductive and nonconductive rubber rubbers used in the rim striprubber 63 and the wing rubber 64 can use the rubber compositionsdescribed in the first embodiment. Therefore, the description regardingformulation contents such as its rubber component and the amount ofcarbon black is omitted in the present embodiment.

In the tire 50 shown in FIG. 5, the tread rubber 61 shows a tread ofintegrated structure. In the case that the tread part 53 has a cap/basestructure, a nonconductive rubber is applied to a cap rubber from thestandpoints of rolling resistance and wet properties. A base rubber canappropriately be selected from a conductive or nonconductive rubber.Other sites such as a topping rubber of a belt and bead filler canappropriately be selected from a conductive or nonconductive rubber solong as a conducting path is not formed. A nonconductive rubber ispreferably selected from the standpoint of the improvement in rollingresistance and wet properties.

In the above embodiment, the invention is described based on the two-plytire comprising two carcass plies. However, it is as a matter of coursethat the invention can be applied to the tire having a one-plystructure, in which one carcass ply is turned back from the inside ofthe tire to the outside thereof around the bead part, reaches theshoulder part 57 through the side wall 56, and is locked.

Fourth Embodiment

A fourth embodiment is such that in a tire 100 using a nonconductive ply90 in which a nonconductive rubber is used in a topping rubber of boththe front and back faces of a carcass ply, on the entire circumference,a conductive path is formed on a part of the nonconductive ply 90 by aconductive rubber.

The conductive path is obtained as follows. For example, a conductiverubber sheet 91 comprising a conductive rubber, having a thickness offrom about 0.2 to 1 mm and a width of from about 2 to 10 cm is laid onthe surface of the topping rubber of the nonconductive ply 90 so as tocontact with a rim strip 93 comprising a conductive rubber and a wing 94exposed to a ground contact edge region in a material preparationprocess of a carcass and a green tire fabricating process. The method isnot particularly limited. Furthermore, the conductive rubber sheet 91may be arranged over both sides between a bead part and a bead part, andmay be arranged in only one side part.

By this, similarly to the embodiments 1 to 3 above, a conducting pathcomprising the conductive rubber sheet 91 is formed in the tire 100, andstatic electricity can be discharged.

FIG. 7 is a tire side schematic view of a tire 100 from which a sidewall rubber was removed, showing the embodiment that a conductive pathis formed in the nonconductive ply 90. A tire 100 a of FIG. 7 (a) showsthe case that plural (8 in the Figure) conductive paths are radiallyformed, a tire 100 b of (b) shows the case that plural (4) conductivepaths are spirally formed, and a tire 100 c of (c) shows the case that aconductive path is helically formed.

EXAMPLES

The present invention is specifically described based on the Examples,but the invention is not construed as being limited thereto.

A conductive rubber and a nonconductive rubber, in which the compoundingamount of carbon black was adjusted, regarding rubber compositions fortopping of a carcass ply, for rim strip and for wing shown in Table 1,and nonconductive rubber compositions for a side wall of carbon blackcompounding and for a tread by silica compounding shown in Table 2 werekneaded and prepared according to the formulations (parts by weight)shown in the Tables by the ordinary method using a Banbury mixer havinga volume of 200 liters. Rubber components and compounding agents usedare as follows. Vol % of carbon black is a calculated value from thecompounding amount (parts by weight).

Natural rubber (NR): RSS #3, made in Thailand

Butadiene rubber (BR): BR150B, Ube Industries, Ltd.

Styrene-butadiene rubber (SBR): 1502, JSR Corporation

Carbon black FEF for ply topping rubber: SEAST SO, Tokai Carbon Co.,Ltd.

Carbon black HAF for rim strip rubber: SEAST 3, Tokai Carbon Co., Ltd.

Carbon black FEF for wing rubber: SEAST SO, Tokai Carbon Co., Ltd.

Carbon black ISAF for tread rubber: SEAST 6, Tokai Carbon Co., Ltd.

Carbon black FEF for side wall rubber: SEAST SO, Tokai Carbon Co., Ltd.

Silica: NIPSIL AQ, Tosoh Silica Corporation

Silane coupling agent: Si69, Degussa

Aroma oil: X-140, Japan Energy Corporation

Paraffin wax: OZOACE-0355, Nippon Seiro Co., Ltd.

Age resistor 6C: NOCRAC 6C, Ouchi Shinko Chemical Industrial Co., Ltd.

Stearic acid: RUNAX S-20, Kao Corporation

Zinc oxide: ZINC WHITE #1, Mitsui Mining & Smelting Co., Ltd.

Sulfur: 5% oil-treated powdery sulfur, Hosoi Chemical Industry Co., Ltd.

Vulcanization accelerator NS: NOCCELER NS-P, Ouchi Shinko ChemicalIndustry Co., Ltd.

Electric resistivity of each rubber composition was measured accordingto JIS K6911, and is shown in Tables 1 and 2. The measurement conditionswere voltage applied: 1,000V, temperature: 25° C., and humidity: 50%.

TABLE 1 Ply topping Rim strip Wing rubber Non Non Non Conductiveconductive Conductive conductive Conductive conductive Formulation NR 8080 70 70 40 40 BR 20 20 30 30 60 60 Carbon black 50 30 70 30 50 30 Aromaoil 10 10 3 3 10 10 Wax 1 1 1 1 Age resistor 1 1 2 2 2 2 Stearic acid 22 2 2 2 2 Zinc oxide 3 3 3 3 3 3 Sulfur 2 2 2 2 2 2 Vulcanizationaccelerator 1.5 1.5 1.5 1.5 1.5 1.5 Carbon black (vol %) 16 12 20 12 1612 Electric resistivity (Ω · cm) 2 × 10⁷ 6 × 10¹² 7 × 10⁶ 2 × 10¹² 2 ×10⁷ 7 × 10¹²

TABLE 2 Side wall Tread rubber Non Non conductive conductive FormulationNR 40 50 BR 60 SBR 50 Carbon black 30 0 Silica 60 Silane coupling agent4 Aroma oil 10 20 Wax 1 3 Age resistor 2 2 Stearic acid 2 2 Zinc oxide 33 Sulfur 2 2 Vulcanization accelerator 1.5 1.5 Carbon black (vol %) 12 0Electric resistivity (Ω · cm) 7 × 10¹² 3 × 10¹³

Radial tires (195/65R15 88S) of one-ply structure as shown in FIG. 1 inwhich a conductive rubber was used in a carcass having a conductive ply,a rim strip rubber and a wing rubber (indicated by “o” in Table 3) or anonconductive rubber was used in a carcass composed of only anonconductive ply, a rim strip and a wing (indicated by “x” in Table 3)were produced according to the combination shown in Table 3, andelectric resistance and rolling resistance were measured by thefollowing methods.

In the tires having a conductive ply of Examples 1 to 4 and ComparativeExamples 3 to 5, a conductive ply was applied in a proportion of thecircumferential length of a tire shown in Table 3. In ComparativeExample 6, a conductive rubber sheet (electric conductivity=2×10⁷ Ω·cm)with carbon black compounding having a thickness of 0.2 mm and a widthof 10 cm was adhered over an area of from a rim strip to a tread,thereby securing conductivity of a tire. Regarding a tread rubber and aside wall rubber, the tread rubber and the side wall rubber shown inTable 2 were commonly used in each tire.

The carcass ply used was a topping sheet obtained by subjecting bothsides of an adhesive-treated tire cord fabric made of a polyester cordof 1670 dtex/2 with counts of 22/25 mm to topping processing in a finishthickness of 1.3 mm using a conductive rubber or a nonconductive rubberfor ply topping shown in Table 1 by a calender apparatus for tire cordfor general production, equipped with Z type calender. The carcass plyhaving conductivity was obtained by jointing a conductive ply having agiven length with a nonconductive ply on a molding drum when fabricatinga green tire.

Furthermore, two plies (cross angle: 45°) of a steel cord of 2+2×0.25structure was commonly used as a belt (count: 18/25 mm), and nylon 66cord of 940 dtex/2 was commonly used as a cap ply (count: 28/25 mm).

Electric resistance of a tire was measured as follows. The tire 10 wasmounted on a standard rim R (15×6JJ) with air pressure of 200 kPa, andthe rim with the tire was attached to a FF type domestic car of 1,600 ccdisplacement. After running the car as trial run at 100 km per hour for3 hours, the electric resistance was measured based on “Measurementprocedures of electric resistance of tire under load” specified in WDK,Blatt 3, Germany. Specifically, as shown in FIG. 10, the tire 10 mountedon the rim was vertically ground-contacted on a copperplate 131 placedon a table plate 130 in an electrically insulated state under a load of400 kg, and electric resistance between the central portion of thestandard rim R and the copper plate 131 was measured using a resistancemeter 132 of applied voltage of 1,000 V. At the time of measurement,temperature is 25° C. and humidity is 50%. The results are shown inTable 3.

The rolling resistance was measured as follows. A tire was mounted on astandard rim with air pressure of 200 kPa, and rolling resistance undera load of 400 kg at 60 km per hour was measured using a uniaxial drumtester for measurement of rolling resistance. The result was indicatedby an index as the value of Comparative Example 1 being 100. The largervalue indicates that rolling resistance is higher and fuel consumptionproperty is poorer. The results obtained are shown in Table 3.

TABLE 3 Position of Comparative side Example 1 Example 2 Example 3Example 4 Example 1 Carcass ply — ∘ ∘ ∘ ∘ x Proportion of —  50  50  50 25 — conductive ply (%) Rim strip Serial side ∘ ∘ ∘ ∘ x Antiserial side∘ x x ∘ x Wing rubber Serial side ∘ ∘ x ∘ x Antiserial side ∘ x ∘ ∘ xElectric resistance  1  5  5  7 10,000 (10⁶ Ω) or more Rollingresistance 104 102 102 103 100 (Index) Position of ComparativeComparative Comparative Comparative Comparative side Example 2 Example 3Example 4 Example 5 Example 6 Carcass ply — x ∘ ∘ ∘ x Proportion of — — 50  50 9 — conductive ply (%) Rim strip Serial side ∘ x ∘ ∘ ∘Antiserial side ∘ x ∘ ∘ ∘ Wing rubber Serial side ∘ x x ∘ ∘ Antiserialside ∘ x x ∘ ∘ Other *1 Electric resistance 10,000 10,000 10,000 8,000 2(10⁶ Ω) or more or more or more Rolling resistance 102 102 103 101 110(Index) *1: A conductive rubber sheet was adhered to the surface of theside wall at both sides over an area of from a rim strip to a tread.

INDUSTRIAL APPLICABILITY

The pneumatic tire of the present invention can be used in variousvehicles such as four-wheel cars such as passenger cars, andadditionally two-wheel cars such as motorcycles, three-wheel cars, andfive-wheel or more buses, trailers and industrial vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a semi-sectional view of a pneumatic tire of a firstembodiment.

FIG. 2 is a tire side view of a first embodiment in which a side wallrubber was cut off.

FIG. 3 is a semi-sectional view of a pneumatic tire of a secondembodiment.

FIG. 4 is a tire side view of a second embodiment in which a side wallrubber was cut off.

FIG. 5 is a semi-sectional view of a pneumatic tire of a thirdembodiment.

FIG. 6 is a tire side view of a third embodiment in which a side wallrubber was cut off.

FIG. 7 is a schematic view of a tire side face of a fourth embodiment inwhich a conductive path was formed.

FIG. 8 is a schematic view showing the measurement method of electricresistance of a tire.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   -   10: Pneumatic tire    -   11: Bead part    -   12: Bead core    -   13: Tread part    -   14: Carcass    -   14X: Conductive ply    -   14Y: Nonconductive ply    -   16: Side wall part    -   19: Rim strip    -   24: Wing

1. A pneumatic tire comprising a carcass having at least one carcass plywhich is locked at a pair of bead parts, a rim strip provided in each ofthe bead parts and contacting with a rim and the at least one carcassply, and a wing in which one edge thereof is contacted with the at leastone carcass ply and the other edge thereof is exposed to the surface ofa ground contact edge region of a tread part; wherein the at least onecarcass ply includes an organic fiber cord covered with a coveringrubber, and the at least one carcass ply includes, as at least thecovering rubber at the contact face side to the rim strip and the wing,a conductive ply comprising a conductive rubber material and anonconductive ply comprising a nonconductive rubber material on thecircumference of the tire, the conductive ply and the nonconductive plybeing a topping rubber attached by topping processing to the surface ofa fabric made of the organic fiber cord, and the conductive ply beingarranged at one place or two or more places in a circumferentialdirection of the tire and extending from a part in contact with the rimstrip to a part in contact with the wing, and the conductive ply and therim strip and the wing in at least one side part form a continuousconductive path comprising a conductive rubber material, only theconductive path is used as a conducting path of the tire, and membersother than the conducting path are selected and used from a conductiverubber material or a nonconductive rubber material.
 2. The pneumatictire as claimed in claim 1, wherein the conductive ply occupies from 10to 50% of the circumferential length of the tire over between the pairof the bead parts.
 3. The pneumatic tire as claimed in claim 1, whereinthe carcass comprises at least one carcass ply which is turned back fromthe inside of the tire to the outside thereof around a pair of beadcores and locked, both front and back faces of the carcass ply arecovered with the conductive rubber, and the turned back portion of thecarcass ply is contacted with the rim strip.
 4. The pneumatic tire asclaimed in claim 1, wherein the carcass comprises at least one firstcarcass ply which is turned back from the inside of the tire to theoutside thereof around a pair of bead cores and locked, and a secondcarcass ply which reaches the bead parts through a side wall part fromthe tread part, contacts with the rim strip, and is locked, and a secondcarcass ply covering rubber of a tire outside face of the second carcassply comprises a conductive rubber material.
 5. The pneumatic tire asclaimed in claim 1, wherein the carcass comprises at least one carcassply which is turned back from the inside of the tire to the outsidethereof around a pair of bead cores and locked, and the carcass ply atthe inner face side of the carcass is extended to the wing outward in aradial direction of the tire while contacting with the rim strip tocontact with the wing, and is locked, in the turned back portion.
 6. Thepneumatic tire as claimed in claim 1, wherein the conductive rubbermaterial is a rubber composition having electric resistivity less than10⁸ Ω·cm.
 7. The pneumatic tire as claimed in claim 6, wherein theconductive rubber material comprises a rubber composition comprising adiene rubber as a rubber component, and carbon black having a nitrogenadsorption specific area of from 25 to 100 m²/g in an amount of 14 vol %or more of the entire rubber composition.
 8. The pneumatic tire asclaimed in claim 1, wherein the nonconductive rubber material comprisesa rubber composition containing a non-carbon black reinforcing agent asa reinforcing agent.
 9. The pneumatic tire as claimed in claim 8,wherein the non-carbon black reinforcing agent is silica.
 10. Thepneumatic tire as claimed in claim 1, wherein at least a portion of thecarcass ply that contacts the wing, the sidewall and the rim stripalternates in conductivity from being conductive to being nonconductiveto being conductive a plurality of times around the circumference of thetire, in segments that are arranged diametrically from a wing portion toa rim strip portion.
 11. The pneumatic tire as claimed in claim 1,wherein the conductive ply extends in a curved manner at an angle to aradial direction of the tire, and the curved conductive ply is arrangedat a plurality of places in a circumferential direction of the tire. 12.The pneumatic tire as claimed in claim 1, wherein the conductive ply ishelically formed from the part in contact with the rim strip to the partin contact with the wing.
 13. The pneumatic tire as claimed in claim 1,wherein the rim strip and the wing in one side part are made of aconductive rubber material, and the rim strip and the wing in the otherside part are made of a nonconductive rubber material.
 14. The pneumatictire as claimed in claim 1, wherein in one side part, the rim strip ismade of a conductive rubber material and the wing is made of anonconductive rubber material, while in the other side part, the rimstrip is made of a nonconductive rubber material and the wing is made ofa conductive rubber material.
 15. A pneumatic tire comprising a carcasshaving at least one carcass ply which is locked at a pair of bead parts,a rim strip provided in each of the bead parts and contacting with a rimand the at least one carcass ply, and a wing in which one edge thereofis contacted with the at least one carcass ply and the other edgethereof is exposed to the surface of a ground contact edge region of atread part; wherein the at least one carcass ply includes an organicfiber cord covered with a covering rubber, and the at least one carcassply includes, as at least the covering rubber at the contact face sideto the rim strip and the wing, a conductive ply comprising a conductiverubber material and a nonconductive ply comprising a nonconductiverubber material on the circumference of the tire, the conductive plybeing arranged at one place or two or more places in a circumferentialdirection of the tire and extending from a part in contact with the rimstrip to a part in contact with the wing, the carcass comprises at leastone first carcass ply which is turned back from the inside of the tireto the outside thereof around a bead core embedded in each of a pair ofthe bead parts and is locked, and a second carcass ply which reaches thebead parts through a side wall part from the tread part, contacts withthe rim strip and is locked without being turned back around the beadcore, the second carcass ply includes, as the covering rubber of thetire outer face side thereof, the conductive ply which contacts with therim strip and the wing, the conductive ply is not provided in the firstcarcass ply and the tire inner face side of the second carcass ply, andthe conductive ply and the rim strip and the wing in at least one sidepart form a continuous conductive path comprising a conductive rubbermaterial, only the conductive path is used as a conducting path of thetire, and members other than the conducting path are selected and usedfrom a conductive rubber material or a nonconductive rubber material.16. The pneumatic tire as claimed in claim 15, wherein the rim strip andthe wing in one side part are made of a conductive rubber material, andthe rim strip and the wing in the other side part are made of anonconductive rubber material.
 17. The pneumatic tire as claimed inclaim 15, wherein in one side part, the rim strip is made of aconductive rubber material and the wing is made of a nonconductiverubber material, while in the other side part, the rim strip is made ofa nonconductive rubber material and the wing is made of a conductiverubber material.
 18. A pneumatic tire comprising a carcass having atleast one carcass ply which is locked at a pair of bead parts, a rimstrip provided in each of the bead parts and contacting with a rim andthe at least one carcass ply, and a wing in which one edge thereof iscontacted with the at least one carcass ply and the other edge thereofis exposed to the surface of a ground contact edge region of a treadpart; wherein the at least one carcass ply includes an organic fibercord covered with a covering rubber, and the at least one carcass plyincludes, as at least the covering rubber at the contact face side tothe rim strip and the wing, a conductive ply comprising a conductiverubber material and a nonconductive ply comprising a nonconductiverubber material on the circumference of the tire, the conductive plybeing arranged at one place or two or more places in a circumferentialdirection of the tire and extending from a part in contact with the rimstrip to a part in contact with the wing, the carcass comprises at leastone carcass ply which is turned back from the inside of the tire to theoutside thereof around a bead core embedded in each of a pair of thebead parts and is locked, and the carcass ply at the inner face side ofthe carcass is extended, in the turned back portion, to the wing outwardin a radial direction of the tire while contacting with the rim strip tocontact with the wing, and is locked, the carcass ply includes, as thecovering rubber of the tire outer face side of the turned back portion,the conductive ply which contacts with the rim strip and the wing, theconductive ply is not provided in the tire inner face side of the turnedback portion, and the conductive ply and the rim strip and the wing inat least one side part form a continuous conductive path comprising aconductive rubber material, only the conductive path is used as aconducting path of the tire, and members other than the conducting pathare selected and used from a conductive rubber material or anonconductive rubber material.
 19. The pneumatic tire as claimed inclaim 18, wherein the carcass comprises two carcass plies of a firstcarcass ply and a second carcass ply which are turned back from theinside of the tire to the outside thereof around a pair of bead coresand locked, the first carcass ply at the inner face side of the carcassis extended, in the turned back portion, to the wing outward in a radialdirection of the tire while contacting with the rim strip to contactwith the wing, and is locked, the first carcass ply includes, as thecovering rubber of the tire outer face side of the turned back portion,the conductive ply which contacts with the rim strip and the wing, andthe conductive ply is not provided in the second carcass ply and thetire inner face side of the turned back portion of the first carcassply.
 20. The pneumatic tire as claimed in claim 18, wherein the rimstrip and the wing in one side part are made of a conductive rubbermaterial, and the rim strip and the wing in the other side part are madeof a nonconductive rubber material.
 21. The pneumatic tire as claimed inclaim 18, wherein in one side part, the rim strip is made of aconductive rubber material and the wing is made of a nonconductiverubber material, while in the other side part, the rim strip is made ofa nonconductive rubber material and the wing is made of a conductiverubber material.